1. Field of the Invention
The present invention relates to an optical system such as a camera with an image blur correction function provided with means for detecting vibration that has occurred in the camera and correcting image blur due to the vibration of the camera.
2. Related Background Art
In existing cameras, since all operations important for photographing such as decision of exposure and focusing are automated, even a person who is inexperienced in handling a camera is very unlikely to fail in photographing.
In addition, recently, a system for preventing hand vibration affecting a camera has been studied, and factors causing failure in photographing of a photographer have been almost eliminated.
Here, a system for preventing hand vibration will be described briefly.
Hand vibration of a camera at the time of photographing is usually a frequency of 1 to 12 Hz. As a basic idea for making it possible to take a picture without image blur even if such hand vibration occurs at the time of releasing, vibration of the camera due to the hand vibration has to be detected to displace a correction lens according to a value of the detection. Therefore, in order to realize photographing of a picture without image blur even if vibration of a camera occurs, it is necessary to detect vibration of the camera accurately and, then, correct a change in an optical axis due to hand vibration.
Theoretically, the detection of vibration (camera vibration) can be performed by mounting on a camera a vibration sensor for detecting an angular acceleration, an angular velocity, an angular displacement and the like and vibration detection means for electrically or mechanically integrating output signals of the vibration sensor to output an angular displacement. Then, vibration correcting means for decentering a photographing optical axis is driven based on information of this detection, whereby image blur control becomes possible.
On the other hand, in a digital camera including a digital single-lens reflex camera that has been actively developed recently, there are provided film camera and a display for displaying an image signal obtained from an image pickup element such as a CCD or CMOS sensor as means for checking a subject image during photographing. With such a digital camera, photographing can be performed using either the display or the finder.
In general, as a way of setting the digital camera in holding it by hands to photograph an image, when the finder is used, what is regarded as ideal is a method of tightening both sides to hold the digital camera by both hands in the same manner as holding a silver salt camera and bringing a photographer""s face (eyebrow part) into contact with an eyepiece part of the digital camera when the photographer looks into the finder.
On the other hand, when the display is used, a method of holding the digital camera by both hands to set it in a position where the photographer can easily see the display (20 to 30 cm ahead of the face) is generally used.
As described above, since the digital camera is supported at three points of both the hands and the face in using the finder to photograph an image by the digital camera, the digital camera can be set relatively stably. However, if an image is photographed using the display, since the digital camera is supported only by both the hands as described above and is set in the position 20 to 30 cm ahead of the face of the photographer, both the arms cannot be fixed and a posture of the photographer becomes unstable. Thus, hand vibration, especially vibration of a low frequency over the entire arms becomes large.
As described above, a frequency band of hand vibration is usually regarded as 1 to 12 Hz, and the conventional camera with image blur correction function is usually designed to correct camera vibration of 1 Hz or more. However, the frequency band of hand vibration usually regarded as 1 to 12 Hz assumes the case in which the photographer uses the finder to perform photographing and does not take into account low frequency vibration over the entire arms when the photographer uses the display of the digital camera to perform photographing.
On the other hand, in recent years, patent applications have been filed for an invention in which a camera detects that a photographer becomes prepared for photographing and starts a specific operation of the camera. For example, Japanese Patent Application Laid-Open No. 64-42639 discloses a technique in which light projecting and receiving elements are arranged in an eyepiece part of a camera and the camera detects a photographer""s operation for looking into the eyepiece part by the elements to start auto-focus control. In addition, Japanese Patent Application Laid-Open No. 3-192338 discloses a technique in which a camera judges approach of a face of a photographer by a line-of-sight detection means and, upon detecting that a pupil of the photographer is observing a finder of the camera, starts auto-focus control or the like. In addition, Japanese Patent Application Laid-Open No. 5-107621 discloses a technique in which, upon detecting approach of a photographer by light projecting and receiving elements of an eyepiece part of a camera or line-of-sight detection means, the camera starts an image blur correction operation.
The above-mentioned conventional techniques are for starting the above-mentioned respective operations according to an output of the light projecting and receiving elements of the eyepiece part of the camera or detection results of the line-of-sight detection means. However, those patent applications do not refer to a method of judging whether a photographer is using a finder or a display.
The present invention has been devised in view of the above and other drawbacks, and thus it is an object of the present invention to provide an optical apparatus having a finder and a display that can perform image blur correction satisfactorily even if the finder or the display is used to perform photographing.
In addition, it is another object of the present invention to provide an optical apparatus that can satisfactorily correct low frequency hand vibration in using a display to perform photographing.
In order to achieve the above-described objects, according to the present invention, there is provided an optical apparatus having an optical system, comprising:
a sensor for detecting vibration that is caused in said optical apparatus;
a blur correction unit for correcting blur of an image obtained by said optical system;
a control unit for controlling driving of said blur correction unit according to an output of said sensor;
a finder for observing the image obtained by said optical system, said finder having an eyepiece optical system; and
a display for displaying the image obtained by said optical system,
wherein said control unit changes a vibration detection frequency band depending on whether said finder is used or said display is used.
In particular, the above-described finder is an optical finder.
Further, the above-described finder is an electronic finder for observing the image displayed on said display via said eyepiece optical system.
Still further, when said display is used, the above-described control unit extends the vibration detection frequency band of said sensor to a frequency area lower than that at the time when said finder is used.
The optical apparatus further comprises a detection unit for detecting whether or not a photographer has approached said finder,
wherein the control unit changes a control characteristic of said blur correction unit according to an output of said detection unit.
The optical apparatus further comprises a switch for switching display and non-display states of said display,
wherein said control unit changes a control characteristic of said blur correction unit according to a state of said switch.
Note that more specific applications of the present invention will be apparent in the detailed description of the invention described later.